DESTA Periodical Report - · PDF fileDESTA Periodical Report D6.3 ... 4.5.2 Test results...

© DESTA PROJECT

DESTA Periodical Report D6.3

www.desta-project.eu

Confidentiality CO Deliverable Type R

Project DESTA Project Number 278899

Contact Person Jürgen Rechberger Organization AVL

Phone +43 316 787 3426 E-mail Juergen.rechberger.avl.com

The research leading to these results has received funding from the European Union’s Seventh Framework Programme

(FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement n° 278899

http://www.desta-project.eu/

DESTA Periodical Report

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Table of Contents

1 Introduction, ......................................................................................................................................... 5

2 Publishable Summary ............................................................................................................................ 5

3 Project objectives for the period .......................................................................................................... 8

4 WP3 – Stack Optimization – Work progress and achievements during the period.............................. 8

4.1 Objectives .................................................................................................................................... 8

4.2 Overall progress in the first period of the project ....................................................................... 8

4.3 Task 3.1 - Delivery of stacks for system evaluation ..................................................................... 8

4.4 Task 3.2 - Durability and Lifetime optimization........................................................................... 9

4.4.1 Overview of lifetime tests ..................................................................................................... 9

4.4.2 Thermal cycling test with power operation ........................................................................ 11

4.5 Task 3.3 - Diesel operation ........................................................................................................ 12

4.5.1 Improved analysis tool ........................................................................................................ 14

4.5.2 Test results with anode modifications ................................................................................ 15

4.5.3 Recommendations for the stack operation strategy .......................................................... 17

4.6 Task 3.4, Delivery and integration of next generation stacks for truck APU ............................. 18

4.6.1 Improvement of gaskets, September 2012 ........................................................................ 18

4.6.2 Change of interconnect design ........................................................................................... 19

4.6.3 Final stack design ................................................................................................................ 20

4.7 Results and achievements ......................................................................................................... 24

4.8 Deviations and corrective actions ............................................................................................. 24

4.9 Conclusions ................................................................................................................................ 25

4.10 Interactions between WP’s ....................................................................................................... 26

4.11 Use of Person Months ............................................................ Fejl! Bogmærke er ikke defineret.

List of Figures

FIGURE : EBERSPÄCHER PROTOTYPE (C) CCES .......................................................................................................................... 5

FIGURE : AVL PROTOTYPE (C) AVL ........................................................................................................................................ 5

FIGURE : DESTA VALUE CHAIN (C) DESTA .............................................................................................................................. 6

FIGURE : THE STACK MODULE AND THE BOXER CONFIGURATION USED IN THIS APPLICATION, SHOWING THE ELECTRIC TERMINALS AND THE

AIR AND FUEL INLETS/OUTLETS. ..................................................................................................................................... 9


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FIGURE 2: CELL GROUP VOLTAGES MEASURED EACH TIME STACK “O” REACHES IT’S REFERENCE CONDITIONS DURING A 90 THERMAL CYCLE

TEST. FOR EACH THERMAL CYCLE, THE STACK WAS TAKEN THROUGH FEW OPERATING POINTS. AFTER ELIMINATION OF ONE OF THEM,

THE CYCLE TIME WAS 3 HOURS, AND THE TEMPERATURE CYCLED BETWEEN OPERATION AND COLD (100°C). .............................. 11

FIGURE 1: TREND OF (A) CELL POTENTIAL AND (B) EXIT GAS COMPOSITION UPON INCREASING THE CONCENTRATION OF H2S SHOWING THE

EFFECT OF INHIBITING THE WATER GAS SHIFT REACTION. .................................................................................................. 13

FIGURE 3: EQUIPMENT AND ITS GENERAL CHARACTERISTICS. ..................................................................................................... 15

FIGURE 4: IMPROVEMENTS IN CELL POTENTIAL FOR VARIOUS GENERATION OF CELLS, ALL OPERATING AT 270 MA/CM2 AND 60% FU ..... 16

FIGURE 5: LONG TERM TESTS OF STACKS ON DIESEL REFORMATE WITH SULFUR. SOME OF THESE TESTS HAVE BEEN FUNDED BY THE SCOTAS

PROJECT. ................................................................................................................................................................ 17

FIGURE 6: DROP IN CELL POTENTIAL OVER TIME FOR TWO STACKS(GEN 4) IN SIMULATED ULSD REFORMATE FEED WITH SULPHUR. ......... 18

FIGURE 6: THE STACK MODULE AND THE BOXER CONFIGURATION USED IN THIS APPLICATION, SHOWING THE ELECTRIC TERMINALS AND THE

AIR AND FUEL INLETS/OUTLETS. ................................................................................... FEJL! BOGMÆRKE ER IKKE DEFINERET.

FIGURE 7: THE STACK IN A MODULE AND THE GASKET BETWEEN THE STACK CORE AND THE INTERFACE PLATE. ...................................... 19

FIGURE 8: THE INTRODUCTION OF THE TSP STACK GEOMETRY IN FEBRUARY 2013. ....................................................................... 20

FIGURE 9: THE LAYOUT OF FUEL INLETS AND OUTLETS IN THE TSP1 STACK. THE CORRESPONDING BOXER MANIFOLD DESIGN IS ALSO SHOWN

HERE. .................................................................................................................................................................... 20

FIGURE 10: LEAKAGE SOLUTION FOR STACK IN SUMMER 2013. ................................................................................................. 21

FIGURE 11: LEAKAGE SOLUTION FOR STACK IN SPRING 2014. .................................................................................................... 21

FIGURE 12: IMPROVEMENTS ON LEAK AFTER CHANGE IN LEAKAGE SOLUTION. ............................................................................... 22

FIGURE : EFFORTS WP3..................................................................................................... FEJL! BOGMÆRKE ER IKKE DEFINERET.

List of Tables

TABLE 1. OVERVIEW OF RELEVANT LIFETIME TESTS FOR THE DESTA PROJECT. WITHOUT SULPHUR. .................................................. 10

TABLE 2. OVERVIEW OF RELEVANT LIFETIME TESTS FOR THE DESTA PROJECT. WITH SULPHUR. ........................................................ 12

TABLE : WP3 PERSON MONTH - EXPLANATION ON DEVIATION .................................................. FEJL! BOGMÆRKE ER IKKE DEFINERET.

Abbreviations

Abbreviation Long Version

APU Auxiliary Power Unit

AUTOSAR AUTomotive Open System ARchitecture

CAN Controller Area Network

DC Direct Current

DESTA Demonstration of 1st European SOFC Truck APU

ECU Electric Control Unit

EMC Electric Magnetic Compatibility

FC-APU Fuel Cell Auxiliary Power Unit

HW Hardware

Ppm Parts Per Million

SOC State Of Charge

V Volt


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Main Authors

Person Organisation

Jonas Hagerskans VOLVO

Christoffer Greisen TOFC

Ingrid Kundner AVL

Jürgen Rechberger AVL

Andreas Kaupert CCES


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PROJECT PERIODIC REPORT

Contribution by TOFC, Christoffer Greisen, October 10, 2014

FCH JU Grant Agreement number: 278899

Project acronym: DESTA

Project title: Demonstration of 1st European SOFC Truck APU

Funding Scheme: FCH-JU

Date of latest version of Annex I against which the assessment will be made:

Periodic report: 1st 2nd

Period covered: from 01.01.2012 to 15.10.2014

Name, title and organisation of the scientific representative of the project's coordinator:

DI Jürgen Rechberger, Manager Fuel Cell, AVL List GmbH

Tel: +43 316 787 3426

Fax:

E-mail: [email protected]

Project website address: www.desta-project.eu


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1 Introduction, Due to the closure of TOFC, this report is intended to serve either as an appendix to the final report, or

as a final technical report from TOFC in order to secure acceptance that all obligations are fulfilled with

only minor deviations. This acceptance has been given to TOFC at a Steering Comittee meeting in

Göteborg on October 8, 2014.

2 Publishable Summary On 1st of January 2012, the research project DESTA

started under the coordination of AVL List GmbH

(Austria). It is the goal of DESTA to demonstrate the

first European Solid Oxide Fuel Cell (SOFC) Auxiliary

Power Unit (APU) on board of a heavy duty truck.

By gathering the project partners Eberspächer

Climate Control Systems GmbH & Co. KG

(Germany), AVL List GmbH (Austria), Volvo (Sweden), Topsoe Fuel Cell (Denmark) and

Forschungszentrum Jülich (Germany) into one consortium, a 100% European value chain for a SOFC APU

is established. With the aim to reduce emissions, noise and costs, the end product will have excellent

export opportunities, creating new high- & clean teach job opportunities in Europe.

A significant advantage of the SOFC technology in contrast to other fuel cell technologies is its

compatibility with conventional road fuels like diesel. The DESTA partners Eberspächer and AVL put a lot

of effort in bringing the SOFC APU technology to a prototype level (see Figure 1 and Figure 2). For a

market entry of this technology, the final breakthrough milestone is the demonstration of its

functionality on a truck; the major goal of the DESTA project.

Figure 1: Eberspächer prototype (c) CCES

Figure 2: AVL prototype (c) AVL

The first phase of the project defines the requirements for the application of a SOFC APU in a Volvo

heavy-duty truck for the US market. Based on test results including production costs, controllability and

manufacturability of the existing systems from AVL and Eberspächer, a benchmark will be performed by


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the independent research institute Forschungszentrum Jülich. During the course of the project, Topsoe

Fuel Cell has worked on the SOFC stack optimization and deliveries of stacks to both integrator partners

as needed. By time of writing, the consortium is confident that the stacks delivered by TOFC are

sufficiently mature and available in sufficient amoun to perform a truck demonstration in late 2014 or

early 2015.

Figure 3: DESTA value chain (c) DESTA

Objectives

The main objective of DESTA is the demonstration of the first European Solid Oxide Fuel Cell (SOFC)

Auxiliary Power Unit (APU) for trucks:

Maximum electrical power ≥3kW

Operation on conventional road diesel fuel

Long-term tests: ~ 300 thermal cycles and ~ 3.000 operating hours

System electrical net efficiency around 35%

System volume and weight below 150 l and 120 kg

CO2 reduction of 75% compared to engine idling of a heavy-duty truck

Start-up time of ~30min

Noise level ~65dB(A)

Truck integration

Achievements to date


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In late 2012 and early 2013, TOFC reached significant improvements of the stacks towards sulfur

tolerance, operation on fuel compositions similar to what is seen in an APU system and thermal cycles.


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3 Project objectives for the period All stack deliveries have been completed

All technical deliverable reports have been submitted.

4 WP3 – Stack Optimization – Work progress and achievements during

the period

4.1 Objectives The objectives of this work package are to design, manufacture/produce, test, ship, and integrate SOFC

stacks optimized for diesel applications and the fully integrated mobile APU system and its durability

and performance objectives.

4.2 Overall progress in the first period of the project In the first half of the project the activities centered on delivering stacks to the two integrator partners,

AVL and Eberspächer. The stack need changed, as it turned out that it would not be possible to meet the

requirements developed in WP1 with a single stack system. Hence, a manifold for a boxer configuration

of two stacks was developed and the number of stacks to be supplied was adjusted.

On the testing side, analysis early in the project showed that the weakest point in the stack module

construction was actually the gaskets inside the stack module. A rapid thermal cycling test in which EAP

is used for stack protection has been used to screen solutions to these gasket issues. The current status

is that the gasket isolating the stack core from the stack module is robust and fulfills its requirements.

A change of interconnect was implemented in March 2013. The new interconnect had been developed

for TOFC’s stationary applications in other projects and had shown good results.

4.3 Task 3.1 - Delivery of stacks for system evaluation The aim of this task was to supply stacks for the system evaluation. During the project it turned out that

the systems would not reach 3 kW on a single stack, provided the gas composition to be expected.

Hence it was acknowledged that more stacks were needed. A total of 16 stacks were delivered in this

phase.

TOFC stacks are based on planar anode supported cells with metallic interconnects. The stack design

used for APU applications has a side air manifold and internal fuel manifolding and is integrated into a

stack module.


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Figure 4: The stack module and the boxer configuration used in this application, showing the electric terminals and the air and fuel inlets/outlets.

This includes a cast casing containing:

(1) A high temperature compression system, that holds the stack itself in place, ensures mechanical

integrity and secures tightness of the gaskets inside the module.

(2) A flat interface allowing for bolting on to the system, either as a single stack, or – for the DESTA

systems – in a twin/boxer configuration.

(3) Electrical isolation of both terminals of the stack itself, so that the casing can be connected to

vehicle ground and allowing for galvanic isolation of the high voltage part of the system.

(4) Power outlet feedthroughs.

(5) Voltage probe feedthroughs, connecting to some of the interconnects in the stack. These allow for

diagnostics during development.

With the design of the stack module, the air flow to the stack also functions as a purge flow around the

stack, ensuring that any leaking fuel is picked up by the air flow and fed to the burner. Hence the design

with external air eliminates any safety concern related to possible leaks.

4.4 Task 3.2 - Durability and Lifetime optimization The stacks have been tested under a number of operating conditions to ensure their performance and

mechanical integrity under harsh thermomechanical stresses. To this end, two gases are used: One

composition resembles the real fuel expected in the APU system. The other ogas is a reforming fuel

based on CH4, which will subject the stack to thermomechanical stresses due to the cooling effect when

CH4 and water is reformed inside the stack to form CO and H2.

4.4.1 Overview of lifetime tests

In table 1 all the relevant stack testing done at TOFC within the DESTA project are shown. The tests

shown here are test without sulfur in the fuel, and the tests includes both QA, robustness, and lifetime

(degradation) tests.


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Table 1. Overview of relevant lifetime tests for the DESTA project. Without sulphur.

Stack (TOFC)

Stack No. of cells

Hot test time (hours)

Load cycles in reforming fuel

Load cycles in H2 based fuel

Thermal cycles

Comments

R-011 A 84 1596 - - 8 Degradation test. Tested outside DESTA project. Current 35 A during test.

R-028 B 84 130 - 15 6 QA test.

R-033 C 84 42 - 5 2 QA test.

R-035 D 80 19 - 8 50 Led to design improvement.

R-040 E 80 145 - 10 115 Lost only 0.1 V of 63 V in 110 thermal cycles

R-042 F 84 25 - 5 2 QA test.

R-044 G 84 600 - 20 97 Thermal cycle test. Led to design improvement.

R-045 H 84 97 - 15 5 QA test.

R-050 I 84 883 - 10 61 Degradation test. Taken apart for analysis of micro defects.

Q-188 J 75 66 10 10 2 QA test. First TSP-1 stack in DESTA project.

Q-220 K 65 475 10 10 5 QA test.

Q-222 L 75 940 10 10 28 Degradation test.

Q-235 M 75 132 20 20 4 QA test.

Q-332 N 75 43 5 5 2 QA test.

Q-401 O 75 190 - - 90 Thermal cycle test.

Q-466 P 75 600 5 5 4 Degradation test. Anode modification.

Q-467 Q 75 1219 5 5 4 Degradation test. Anode modification. Stack is still in good shape.

Q-539 R 75 2500 27 5 12 Degradation test. Anode modification. Stack is still in good shape.


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To verify that the stacks are fit for the application including a weekly full cooldown and heatup, an

accelerated test method has been developed so that a full thermal cycle can be completed in less than 4

hours. With this test it was shown that the stacks can withstand more than 100 thermal cycles without

any damage.

4.4.2 Thermal cycling test with power operation

One of the stacks with the latest modifications, stack “O”, has endured 90 rapid thermal cycles in a

furnace based test, where the stack is cycled between 25 A operation on a H2/N2 mixture at an

operating temperature (~700°C) and cold conditions (<100 °C).

As seen in Figure 5: Cell group voltages measured each time stack “O” reaches it’s reference conditions

during a 90 thermal cycle test, a stable and almost constant degradation is the dominating effect. The

steps are directly correlated with the change in cathode inlet temperature. After 90 thermal cycles the

spread in cell group voltage is still only 1 %, which indicates that the cycling has done little if any damage

to the stack.

Figure 5: Cell group voltages measured each time stack “O” reaches it’s reference conditions during a 90

thermal cycle test. For each thermal cycle, the stack was taken through few operating points. After

elimination of one of them, the cycle time was 3 hours, and the temperature cycled between operation

and cold (100°C).


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A number of representative test results obtained on full size stacks combining these test methods is

summarized in Table 1.

4.5 Task 3.3 - Diesel operation Table 2. Overview of relevant lifetime tests for the DESTA project. With sulphur.

Stack (TOFC)

Stack No. of

cells

Hot Test time

(hours)

Load cycles in H2 based

fuel

Thermal cycles

Comments

T-038 1 25 2200 - - At 2 ppm and 20 ppm S. in simulated diesel reformate.

K-452 2 25 1100 - 2 At 2 ppm and 25 ppm S. in simulated diesel reformate.

K-570 3 11 900 - 2 At 2 ppm S. in simulated diesel reformate. Regeneration.

K-654 4 11 600 - 2 At 2 ppm S. in simulated diesel reformate. Regeneration.

K-681 5 11 2462 90 4 At 0.6 ppm S. in simulated diesel reformate. Regeneration.

The most important contaminant to consider for diesel operation is sulphur, which main impact is the

poisoning of the water-gas shift reaction in the stack

The tests with sulphur are further elaborated in D.3.3, Fuel tolerance test report.

To accept the sulphur levels of ULSD, the anodes have been modified. These modifications have been

tested on stacks with 11-25 cells. The anode modification has been implemented and verified in some of

the full size stacks used for developing the two APU systems. For this purpose, several 11 and 25 cell

stacks have been tested upto 20 ppm sulfur in simulated AVL diesel reformate to study the long term

performance (order of 600-2000 h), i.e., degradation of cell potentials. The stack degradation for the

Generation 4 stacks shown in the figure below was reduced to 20 mV/kh by optimizing the cells.


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At the start of the project, using Sc-YSZ in the anode was considered a promising path. However, due to

the scarcity and cost limitations of Sc, it was decided to follow other paths towards sulphur tolerance.

A background IP search was conducted with the assistance of TOFC’s mother company Haldor Topsoe

A/S (HTAS) to find ways to improve the sulfur tolerance of the stacks. The availability of secret know-

how of materials and their processing methods at HTAS allowed us to use the relevant IPs for the

development of sulfur tolerant cells.

A series of materials were screened and characterized for water gas shift activity with and without sulfur

and the most active material was chosen as anode material. In the first step, the water gas shift activity

was studied over powdered Ni anode for various composition of CO, H2O, CO2, H2 and N2 in the gas feed.

A rate expression for water gas shift reaction was developed and impact of sulfur was studied over this

0.0

2.0

4.0

6.0

8.0

10.0

0.1 1.0 10.0 100.0

Sulfur, ppm

Gas

Com

posi

tion

, %

CO

H2

-120

-100

-80

-60

-40

-20

0

0.1 1 10 100 1000

Sulfur, ppm

DV

, m

V

Gen 1

Figure 6: Trend of (top) cell potential and (bottom) exit gas composition upon increasing the concentration of H2S showing the effect of inhibiting the water gas shift reaction.


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rate. It was found that sulfur deactivates the water gas shift reaction instantaneously. Four potential

materials were further investigated for water gas shift activity and the impact of sulfur was studied on

these materials and the one with the best activity for water gas shift reaction in the presence of sulfur

was chosen to modify our anode. The selection of the materials and initial evaluation was supported by

EUDP1. However, the long term effects of the best material were investigated under SCOTAS2 and

DESTA projects.

Anode Material Conversion of CO Sulfur Composition

Ni

Ni

Ni-M1

Ni-M2

Ni-M3

Ni-M4

High (Equilibirium conversion achieved)

Negligible (<1%) at BOL and deactivated over time Deactivated over time Deactivated over time (Necessary phase was probably not obtained) Good shift activity Good shift activity (More than M3)

0

0.3 ppm

0 ppm

0 ppm

0.3 ppm

0.3 ppm

4.5.1 Improved analysis tool

It was of considerable interest to understand the mechanism of interaction of H2S with Ni anode, more

specifically, the composition of sulfur species in the exit gas and the concentration dependence with

current densities, fuel utilization, concentration of H2S in the feed etc. This understanding is important

to improve the sulfur tolerance of the cell. A search was conducted in the market for the appropriate

equipment and large amount of time was spent on shipping of equipment from USA, set-up, safety

protocols, calibration, troubleshooting of the equipment for a proper operation. The tool was

1 , “Fuel Cells Put to Work”, supported by Danish Funding, EUDP, j.nr. 64010-0052

2 SCOTAS: “Sulphur, carbon, and re-oxidation tolerant anodes and anode supports for solid oxide fuel cells”, FCH-

JU, GA 256730


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operational around April 2013, and from this time the development on sulphur tolerance could be

accelerated. A picture and specification of such equipment is shown below.

Figure 7: Equipment and its general characteristics.

4.5.2 Test results with anode modifications

Figure 4 shows the improvements in cell potential for the cells run under simulated diesel reformate

with 0-20 ppm H2S. An improvement of about 160 mV per cell is observed (comparing Gen 4 with Gen


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1) for the conditions relevant to an APU based systems. These improvements are the result of adding

sulfur tolerant shift promoters into the anode microstructure. The modifications have been tested on

stacks with 11-25 cells. The anode modification has been implemented and verified in some of the full

size stacks used for developing the two APU systems. Most of the improvements in the cell potential is

the result of a higher water gas shift activity in the presence of sulfur.

Figure 8: Improvements in cell potential for various generation of cells, all operating at 270 mA/cm2 and 60% FU

The current long term results show that without changes to the operating strategy of the stack, the

degradation rate is too fast to meet the lifetime requirements, even with the improved Gen 4 cell

formulation. The stacks were tested for long term with a gas composition3 given by AVL and higher

sulfur concentration (2 and 20 ppm H2S) than required by DESTA conditions. The results are shown in

the graph below in figure 5. The experiments were run at different conditions of fuel utilization and

current densities to see the effect on degradation and tolerance of the anode towards the sulfur.

3 For detailed composition, please consult D.1.3 APU Stack test standards.

610

630

650

670

690

710

730

750

770

790

810

0,01 0,1 1 10 100

Ce

ll P

ote

nti

al, m

V

Sulfur,ppm

Gen 2

Gen 1

Gen 3

Gen 4

0


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Figure 9: Long term tests of stacks on diesel reformate with sulfur. Some of these tests have been funded by the SCOTAS project.

4.5.3 Recommendations for the stack operation strategy

It is recommended to use a regeneration approach, in which during the daily driving, the system

regenerates the stacks. This regeneration approach was identified through our corporate R&D group.

Operating with such a regeneration approach will lower the degradation rate significantly, as shown in

Figure 6, where it is observed that after application of regeneration strategy for our cells (Gen 4), the

degradation rate of stacks has decreased significantly under simulated ULSD reformate conditions.

700

710

720

730

740

750

760

770

780

790

800

0 250 500 750 1000 1250 1500 1750 2000 2250 2500

Ce

ll vo

ltag

e (

mV

)

Time, h

Gen4/65%/ 225 mA/cm2

Gen4/70%/ 340 mA/cm2

20ppm S

2 ppm S

2 ppm S

Gen4/65 %/250 A/cm2

2 ppm S

Gen4/65 %/300 mA/cm2

0.6 ppm S

2 ppm S

Gen4/70%/ 270 mA/cm2


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Figure 10: Drop in cell potential over time for two stacks(Gen 4) in simulated ULSD reformate feed with sulphur.

One regeneration cycle constitutes a 18 h on full load operation and 4 hours of regeneration on regen

gas at 0 A and 2 hours for the load cycle (0-26-0 A). The regen gas allows the sulfur adsorbed on the

anode to be released in the form of H2S. The amount of sulfur released from the anode depends on the

flow rate of the regen gas, time of regeneration and type of regen gas. A number of tests have been

carried out screening gas compositions that would be possible to obtain the the DESTA demonstrator

system. At they time of writing they have – however – not been successful.

4.6 Task 3.4, Delivery and integration of next generation stacks for truck APU After the initial stack deliveries, a number of improvements were made. In the following these will be

elaborated with reference to the stack numbers and tests.

4.6.1 Improvement of gaskets, September 2012

In September 2012, cycling tests (see Fejl! Henvisningskilde ikke fundet. with stack “G”) showed that

the weak spot was in the gaskets, which was torn apart due to alternating thermal stresses. The gasket

is shown in Figure 11.

700

720

740

760

780

800

820

0 500 1000 1500 2000 2500

Ce

ll P

ote

nti

al, m

V

Time,h

w/o Regeneration

w Regeneration

Characterization conditions

DESTA test conditions


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Figure 11: The stack in a module and the gasket between the stack core and the interface plate.

The conclusion was that smooth surfaces should be redesigned to apply raised faces, or simply

roughened surfaces, also on interface between the stack module and the boxer manifold. Such changes

were implemented in subsequent stacks.

4.6.2 Change of interconnect design

Based on the increased stack demand (2 stacks per system), and in order to improve manufacturability,

it was decided to bring in the interconnect used for TOFC’s stationary applications. The change took

effect in February 2013, and all stacks from “J” and forward are made with this interconnect. The change

is sketched in Figure 12.


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Figure 12: The introduction of the TSP stack geometry in February 2013.

The new design was therefore also used in the last 4 benchmark systems. The TSP interconnect is

formed from thin sheet metal, which gives fewer degrees of freedom for the flow geometries. Hence,

the stack core has 3 fuel inlets and 3 fuel outlets, which can be seen in Figure 13.

Figure 13: The layout of fuel inlets and outlets in the TSP1 stack. The corresponding boxer manifold design is also shown here.

4.6.3 Final stack design

In the final stack design TOFC estimated that is was critical to get the leakage even further reduced, and

hence make the stack even more robust. These changes happened gradually during the fall of 2013 and

the spring of 2014.


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The leakage solution before these major improvements is shown in Figure 14. This consists of both an

inner leakage solution and an outer solution.

Figure 14: Leakage solution for stack in summer 2013.

The improvements made on the design were to change the design of the welded plate and the gasket

layout. On top of that the thickness of the gasket was changed and the design of the surface structure

was improved again. Besides these things the steel inlay in the gasket was also changed. These changes

resulted in a solution that is shown in Figure 15.

Figure 15: Leakage solution for stack in spring 2014.

The improvements turned out to have successfully reduced both the stack core leakage and also the

total leakage when the casing is mounted on a manifold. The actual improvements are shown in

numbers in Figure 16, where the anode leakage flows to maintain 100 mbar is shown in different

scenarios.


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Figure 16: Improvements on leak after change in leakage solution.

These improvements are further elaborated in the deliverable report D3.4

In the following table a complete list of all the stacks delivered from TOFC to the DESTA project is

shown.


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Stack ID Partner Delivery date

Average cell

voltage 25 A

H2 (mV)

Remark

R-021 ECCS 895

R-023 AVL 893

R-024 ECCS 894

R-030 ECCS 895

R-043 ECCS 20-jan 903

R-046 ECCS 20-jan 902

Q-333 ECCS 19-mar 897

Q-334 ECCS 19-mar 897

Q-345 ECCS 17-maj 885

Q-347 ECCS 17-maj 885

R-047 AVL 08-apr 901

R-052 AVL 08-apr 903

Q-342 AVL 03-maj 885

Q-344 AVL 03-maj 885

Q-350 AVL 14-jun 890

Q-400 AVL 07-aug 871

Q-390 ECCS ? 878 "dummy". Not modified

Q-411 ECCS ? 866 "dummy". Not modified

Q-388 ECCS 09-jan 878

Q-389 ECCS 09-jan 872

Q-570 + Q-572 ECCS 09-may 893 ; 893

Q-590 + Q-591 ECCS 23-jul 884 ; 888

Q-387 + Q-466 ECCS 22-sep 830 ; N/A Q-466 Accepted on CH4 operation

Q-624 + Q-612 ECCS 08-oct 904 ; 897

Q-614 + Q-615 ECCS 08-oct 897; 903


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4.7 Results and achievements The main result from the period has been the supply of stacks for system development and the

improvements on gasket and manifold solutions.

D 3.1: Delivery of modified APU stacks: This was completed on time, but accompanied by an agreement

among the partners for the supply of more stacks for the benchmark systems. In total 16 stacks were

delivered for one-stack systems and benchmark systems.

D 3.2: Delivery of optimized stacks: This report was slightly delayed, and also this time it was accepted

by the consortium that the last stacks could be supplied “on demand”. A total of 12 stacks were

delivered to ECCS for integration into the truck demonstrators.

D 3.3: Fuel Tolerance test report: This report was delivered with a minor delay. It did not completely

fulfill the original project ambitions.

D 3.4: Lifetime test report: This report was delivered with a minor delay, but documenting how the

stacks have been made to fit the requirements of the APU systems.

4.8 Deviations and corrective actions In this work package there have been 6 deviations.

(1) Change to two stacks per system: By completion of the requirements report and based on

information on the gas composition to be expected, it was evident that the power would not be

able to be delivered by just one stack. This has generated some more stack deliveries (updated


7/21/2016 Page 25 of 26

plan is to deliver a total of 28 stacks instead of 16 in the DoW). This is addressed in the Annex 1

update, including a budget adjustment agreed among the partners to compensate for this

change. This deviation has been handled with only minor impact on fulfillment of the project

objectives.

(2) Focus on seals in robustness activity: The effort of robustness showed that the weakest point of

the stack is not the stack core, but rather the gaskets. It turned out that the gasket between the

stack modules and the boxer manifold was not sufficiently tight, especially after thermal cycling.

A solution was found. The improvements implemented fixed the problem, so this deviation had

no impact on fulfillment of the project objectives.

(3) Obtained thermal cycles. Over the course of the project it was acknowledged in the consortium,

that 250 thermal cycles should be sufficient for expected operation. However, the tests did not

fully reach this number. 90 cycles was obtained and the stack was still in good shape. So this is

considered to have a minor impact on fullfilment of project objectives.

(4) Anode modifications for Diesel operation: It has been decided not to use Sc-YSZ, but rely on

other modifications of the anode. This has had no impact on other WP’s.

(5) M4: Testing 5000 hours on diesel reformate: Due to difficulties establishing a test that would

operate with a CPO it was decided to run this test on a simulated gas mixture adding controlled

amounts of sulphur. It was done on short stacks with internal manifolding, as the interaction of

sulphur and the cell electrochemistry can be evaluated fairly well on such a test platform. The

test results showed that without changes to the operating strategy of the stack, the degradation

rate is not slow enough to meet the lifetime requirements. Discussions on the implementation

of a regeneration concept had started between ECCS and TOFC, but have not concluded by the

time of TOFC’s exit.

(6) No tests on diesel additives were performed due to the lack of data on how such additives are

have been performed so far. Such additives are heavily transformed in the reformer. As for the

testing with diesel additives, a diligent definition of such tests would have requires a detailed

analysis of the outlet gas from the reformer in question. This information has not been available

for the project.

(7) The closure of TOFC: This will have only minor impact on the fulfillment of project objectives,

but fulfillment of the project purpose is of course affected, since the stacks around which the

demonstrator has been designed, will no longer be available.

4.9 Conclusions With regard to the stack supply to the integrators, the work in the work package has progressed

satisfactory.

With regard to the stack testing, the test time and number of cycles did not reach all the targets, but on

the contrary a larger number of stacks have been tested adding to the confidence that the stacks are fit

for the APU application.


7/21/2016 Page 26 of 26

With regard to sulphur tolerance, it has not been proven that the stacks can endure the full specified

lifetime without losses and a way to implement the regeneration method has not been found.

4.10 Interactions between WP’s The requirements created in WP1 have been used for defining stack tests and deciding that two stacks

were needed.

The collaboration has been rather intense, especially with Eberspächer on the benchmark testing in WP2

and on the testing of the truck demonstrators. This also goes for the packaging studies in which the

design was optimized to accommodate the updates on the stack module design. The recording of cell

group voltages in the development and benchmark tests at Eberspächer allowed TOFC experts to assist

in troubleshooting and adjustment of operating strategies.

Throughtout the project TOFC have assisted both integrator partners with know-how and support about

the stacks are best operated in the APU systems, and there has been on-site tests of the APU systems at

Eberspächer where TOFC stack experts have been present.

Bibliography

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